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Jan.-27, 1931. G. BABCOCK TELEPHONE RECEIVER Filed Oct. 6, 1 26 WELD I 00 0 w w 2 3wm N S 1 /l/. /3 3 6 Garrison Babcack Patented Jan. 27, 1931GARRISON BABCOGK, F SEATTLE, WASHINGTON, ASSIGNOR.T0 AMERICAN TELE-CHRONOMETER ING'ION CQMPANY, OF EVERETT, WASHINGTON, ACORPORATION OFWASH- TELEPHONE RECEIVER Application filed October 6,1926.v Serial110,139,810.

My invention relates to a telephone receiver unit andparticularly to adevice adapted for use in loud speakers to energize a vibratory body forthe reproduction of sound.

in part my present invention is a'continuation of my application SerialNo. 1,052, filed June 26, I922, andin part it is an improvement upon myPatent No. 969,832.

It is an object of my invention to provide an electromagnetic structurehaving a minimum of magnetic reluctance, andapplying the magnetic forcemost effectively and concentratedly to a diaphragm.

Afurther object is the provision of an electromagnetic unit for suchpurpose, and of a diaphrag'un or armature for use in con nectiontherewith by means of which a diaphragm is mounted between two opposedpoles and is thus neutrally positioned in a 1 strong field, to beenergized sensitively by slight variations in the magnetic flux throughsaid field.

A further object is the provision of a simple diaphragm in which thecentral. portion is placed in a highly stressed condition, whereby itsnatural period is above the range of audibility, supported within aflexible ring from a suitable support.

A further object is the provision, in a diaphragm of means to preventthe direct transmission of a sound of given periodicity to any locallyresponsive-portion of the diaphragm, to set up local vibrations there;in other words, it is an object to provlde a dia- I phragm which as awhole and in all portions is in efiect aperiodic.

electromagnetic structure and the improve ment of details of itsmanufacture and mounting.

lvly invention comprises the novel elective-- magnetic structure andmounting and. the novel diaphragm, aswell as the novel combination andarrangement thereof, as shown in the accompanying drawings, described inthe specificatiomand particularly defined by the claims terminating thesame; In the accompanying drawingsI have illustrated a preferredembodiment Of the prim ciples of my invention.

in place the disk 16 cannot A further object is the simplification ofthe .field is concentrated there. circuit is completed through a ableunion joint, shown as threaded annulus 4, secured Figure 1 is an axialsection through the electromagnetic unit and its mounting.

Figure 2 1s a diagram of the electrical and magnetic circuits.

Figures 3, l, and 5 are axial sections illustlitillIlgSllCCGSSlVG stepsin the manufacture of my diaphragm, and Figure 6 is a face View of thediaphragm. I

Figure 7 is a fragmentary elevation of a detail of the electricalconnector block.

As the foundation for my device, I employ two magnetic cores 1 and 10,which are substantially alike, except that the core 10 is provided withan external threaded stem 11 by means of which it may recive a nuttoclamp it to a rigid support 2. For economy thesecores are designed tobe manufactured by an automatic screw machine, and for this purpose eachis provided with a flange 14 at one end. At its opposite end a reducedneck 13 is formed, this fitting tightly within an aperture provided forthis purpose in the respective casing halves or cups 3 and 30. If thisneck does not fit tightly in its cup, or if the contact is poor betweenit and the cup, it can be held more tightly and brought into closercontact by swaging its outer end, as will be obvious. The windings 5 andcan be retained on their respective cores 1 and 10 by securing astifidielectric disk 15 thereon in contact with the flanges 14, andsecuring second dielectric disk 16 thereon at its opposite end, adjacentthe inside of the cup. The disk '16 may be atight fit, to enable thecoils to be wound, but when the core is secured possibly come ofi,inasmuch. as it lies against the inside of its i cup. The windings 5 and50 are preferably so disposed, as shown diagrammatically in Figure 2,that the adjacent poles of the cores 1 and 1'0 are of opposite polarity.

The cups 3 and'3O are of magnetic material and form a double magneticcircuit centering at their respective cores 1 and 10, whereby the Themagnetic type of adjustcomprising the to the casing 3, the flangedannulus 40 secured to the casing half 50, and. the flanged and threadedcom nccting member ll. These members 1, 1O, and 4:1 are good magneticconductors and thus the magnetic circuit is completed from the northpole 1 across the air gap to the south pole 10, thence through themembers 30, s 0, 41, l, and 3 back to the north pole 1.

Supported between the two casing halves and between the two cores 1 and10 is a diaphragm, which preferably is of a peculiar construction, asdescribed hereafter. This is of magnetic material, but inasmuch'as theadjacent poles of the cores are of opposite polarity, and inasmuch asthe magnetic circuit is completed through the casing members, thediaphragm itself will not become saturated but will respond sensitivelyto slight variations in the magnetic field caused by signals impressedupon the circuit through the windings 5 and 50. The diaphragm is sopositioned, with respect to the windings, that it is attracted by onecore simultaneously with its repulsion by the other core, to transmitthe energ 1 thus produced to sounding medium. The cores 1 and 10 may beaxially bored and a link 6 extends from a point of connection to thediaphragm to a connection to any suitable sounding medium, such as thecone 60. The cone 60 may be supported in any suitable or usual manner,and this serves as the actual sound reproducer. The opposite core isareferably apertured also to relieve the back side of the diaphragm fromdampening air pressure variations.

The diaphragm employed consists of a highly tensioned central portionand a supporting annulus, which for the type of unit shown herein ispreferably flexible. It is desirable that the inner portion be so highlystressed that its natural )eriod of vibration is above the range ofaudibility. To accomplish these two result-s, I may employ a compositediaphragm formed of two bulged disks 7, reversed to bring their convenedsides together and then so held as to retain a central area under thestress caused by the flattening of the bulged disks.

Figure 3 shows the two separate, reversed disks. The next step is toconnect the disks, and they are first connected at their centers by aweld, as indicated. at 70. The edges are then brought closer togetheruntil a central area 71 has been flattened. Thus held, the periphery ofthis central portion 71 is delined by welding, as indicated at 72, thusdefinitely and permanently retaining this central. portion 71 under astress which can be made so great that its natural period is above therange of audibility. The stressing of the diaphragm may be secured inany suitable manner, and the construction shown is preferred in thepresent assembly because of the integral flexible mounting which can beformed at the same time. If the assembly with which the diaphragm is tobe used does not require a flexible mounting, the diaphragm might bestressed in the manner disclosed in my application referred to above.

An annular portion of each disk remains free of the stressed centralportion 71 and this, to a large extent, is unstressed. These marginalportions 73, when suitably held about their periphery, form a exiblesupport for the stressed central portion 71. As shown in Figure 1, theannular marginal portions 73 are held in engagement with the peripheriesof the casing members 3 and 30. By adjusting the annular coupling member4C1 the casing members 3 and 30 and their cores 1 and 10 may be broughtcloser together or separated. The ideal condition for greatest volume isas close approach of the two cores as is possible without permittingactual contact of the diaphragm with either core when vibrating at itsgreatest amplitude.

A diaphragm which, as a whole, may have a natural period above the rangeof audimay yet have local areas or points which will vibrate in sympathywith tones within the range of audibility, and which will persist. Thusa persisting tone will mingle with and affect a following tone, and inorder to prevent this interference and to render the diaphragm trulyaperiodic within he range of audibility, I prefer so to form its centralportion 71 as to break up or prevent ready communication between thepoint 76 of application of its force and a locally vibratory point. Tothis end, after the two halves have been welded together, as shown inFigure 4. I may crimp the two halves as indicated in Figures 5 and 6.The crimp has been shown in Figure 6 to take the form of a spiral T5,started at the central point 76 of thediaphragm and terminating at thewelded periphery 72 of the central portion 71. This crimp being evenmore highly stressed than the general plane of the central portion 71,breaks up and prevents direct communication between any local area andthe point of application of the force, and so delays communicationbetween two such points that no interference results. The effect is of adiaphragm flexibly supported about its periphery and vibrating as awhole, without any periodicity of its own, in response to impulses ofany periodicity within the range of audibility.

hat I claim as my invention is:

1. In a sound source, the combination with a sound impulse source. of adiaphragm operath ly within the influence of said source, and responsiveto vibrations thereof, said diaphragm being stressed to give it anatural period above the limit of audibility.

In combination, a sound impulse source, a diaphragm connected to saidsource and responsive to vibrations thereof, said diaphragm beingstressed to give it a natural period above the limit of audibility, andhaving means to eliminate direct communication between the area ofapplication of the 'core principle energizing torces and locallyvibratory areas; 7 3.111 combination, a diaphragm having a central areastressed to give it a natural period above the limit of audibility, andsup porting meansabout the periphery of said central area.

4;. In combination, vibratory diaphragm having a central area stressedto give it-a I natural period above the limit of audibility,

nu'lar. flexible supportsextending at each side or" the plane of thecentral area.

6. In a telephone-receiver, in combination, a casing comprising twohalves, a central between said cores, and means for suppor ing saiddiaphragm from the casing and for adjusting the air. gap between saidcores, to

maintain the diaphragm at all adjustments equally spaced from the twocores. y

7. In a telephone receiver, in combination,

a casing. comprising two halves, a vcentral core. projecting from eachof said casing halves towards the other core toleave an air gaptherebetween, means connecting said halves for relative axial adjustmentto vary the air gap between the cores, a diaphragm equidistant betweenSaid casinghalves and their cores, and means for maintaining thediaphragm always equidistant from the cores for any relative adjustmentthereof;

8. In a telephone receiver, in combination, a casing comprising twohalves, a central .core projecting. from, each half toward, the oppositecore, and spaced therefrom to leave an air gap. means connecting saidhalvesfor relative axial adjustment to vary the airigap between thecores, and a diaphragm comprising a generally plane centralarea coaxialwith and positioned betweengthe cores and.

a peripheral support engaged by the casing halves and yieldable axiallythereof, whereby the central area oi the diaphragm isv maintainedequidistant from the two cores. as the air gap therebetween is varied.

7 9. In a telephonereceiveiyin combination, a magnetic casing comprisingtwo cup-like members having their rims spaced from each other, andmagnetically connected, an axial core secured ineach half and projectingto- 'wards but spaced from the opposite core, a

coil associated with each casing half to maintain the adjacent ends ofthe cores of opposite polarity, and a diaphragm intersecting the strongmagnetic field thus formed between the cores, and equidistantly spacedbetween said cores.

10. In a telephone receiver, in combination,

projecting from each of said casing halves towards the other' core toleave an air gap therebetween, a diaphragm positioned .formed tointerrupt local vibrations tendina magnetic casing comprising twocup-like members having their rims spaced from each other, andmagnetically connected, an axial core secured in each half andprojecting to- Wards but spaced from the opposite core, a coilassociated with each casing half to maintain the adjacent cndsnf thecores of opposite polarity, and a diaphragm intersecting the strongmagnetic field thus formed between the cores, and equidistantly spacedbetween said cores, and means for adjusting the air gap between saidcores, theidiaphragm be ng always maintained equidistant from the cores.

11 In a telephone receiver, in combination, 7 a casinghavmg acentral'aperture, a shouldered core having its reduced portion receivedin said aperture, a flange on the end of said core, an apertured' disksupported on said coreand abutting against said flange. and a coil woundupon said core between the cas ing and said disk.

1 12. In a telephone receiver, in combination, a casing having a centralaperture, an axially bored core having a reduced end tightlyreceivedinsaid aperture, a flange on said core opposite its reduced end, anapertured dielec- ,tricdiSk. supported on said core and abutting againstsaid flange, a second dielectric disk on said core and abutting againstsaid casing, and a coil wound on said core between said disks.

13. A, diaphragm comprising a central area and integral peripheralsupports. said central area'being initially stressed to attain a naturalperiod above the range of audibility, and said supports beingnormally'unstressed, and flexible in an axial direction.

14. A. diaphragm comprising a central area and integral peripheralsupports, said central area being initially stressed to attain a naturalperiod above the range of audibility, and said supports being normallyunstressed, and flexible in an axial direction, means for attaching alink to said-central area, and said central area being disposedandtoemanate from said link-attaching means. 15. A diaphragm comprising acentral area and integral peripheral supporta'said central area beinginitially stressed to attain a natural'periodabove the rangeofaudibility, and said supports beingnormally unstressed, and flexible inan axial direction, a sound impulse source oisposed adjacent the centerof said'diaphragm to actuate the same,

and said central area being disposed and' formed tointerruptlocalyibrations in the diaphragm tending to radiate from the region ofapplication of the greatestapplied force.

disks placed'back to back and connected along 'a' circleoutward of theircenters to. maintain each disk outward of such circles being left freeand unconnected.

17. A diaphragm comprising two bulged disks placed back DO back andconnected at their centers and along a circle outward therefrom, butinward of their peripheries, to maintain them str- 18. A diaphragmcomprising two bulged disks placed back to back and connected at theircenters and along a circle outward therefrom, but inward of theirperipheries, to maintain them stressed, the area within said circlebeing deformed to interrupt local vibrations.

19. A diaphragm comprising a unitary central area initially stressed tohave a natural period above the range of audibilit and peripheralsupporting means therefor.

20. A diaphragm comprising a unitary central area initially stressed tohave a natural period above the range of audibility, and peripheralsupporting means therefor, said supporting means being normallyunstressed and yieldable.

21. A diaphragm comprising a unitary central area initially stressed tohave a natural period above the range of audibility, and peripheralsupporting means therefor, comprising a pair of diverging flexibleannuli integral with the central area but normally unstressed.

22. In combination, a diaphragm comprising a unitary central areainitially stressed to have a natural period above the range ofaudibility, peripheral supporting means therefor comprising a pair ofdivergent flexible annuli extending about the central area, and a casingcomprising two cup-like halves and means for adjusting said halvestowards and from each other in an axial direction, said annuli beingreceived each in its respective casing half to maintain the diaphragm inlike relation to each half for any adjustment thereof.

23. The process of manufacturing a diaphragm which comprises securingtogether the centers of two bulged disks, placed back to back, stressingsaid disks by pressing them together to contact throughout a centralarea, and finally securing said disks about the periphery of saidcentral area to maintain the same under stress.

24. The process of manufacturing a diaphragm which comprises pressingtogether two bulged disks, placed back to back, to contact throughout acentral area, then per manently securing said disks about the pe ripheryof said area, to maintain said area stressed to a degree where itsnatural period is above the range of audibility.

25. The process of manufacturing a diaphragm which comprises pressingtogether two bulged disks, placed back to back, to contact throughout acentral area, then permanently securing said disks about the peripheryof said area, to maintain said area stressed to a degree where itsnatural period is above the range of audibility, and finally deformingsaid central area to interrupt local vibrations.

26. The process of manufacturing a diaphragm which comprises pressingtogether two bulged disks, placed back to back, to contact throughout acentral area, then permanently securing said disks about tie peripheryof said area, to maintain said area stressed to a degree where itsnatural period is above the range of audibility, and finally crimpingsaid central area spirally about the point of attachment to the same.

27. An electromagnetic structure comprising an apertured casing, amagnet core having a flanged end and having its opposite end adapted forsecurement in said aperture of the casing, a disk secured upon said coreand retained by the flange thereon, a second disk secured upon theopposite end of said core, and elec 'ric windings about said corebetween said disks, and means upon the end of said core which is securedto the casing, and externally thereof, for supporting said electromagnetic structure.

28. In. a. telephone receiver, in combination, a casing, anelectromagnet therein, and a diaphragm supported in said casing adjacentsaid magnet, and comprising a supporting ring of magnetic material, anda stressed diaphragm supported in said ring and eX- tending over saidmagnet.

29. A diaphragm comprising an outer supporting annulus and a centralportion stressed to give it a natural period above the range ofaudibility.

30. A diaphragm comprising a central portion having a sharply definedperiphery, and stressed to give it a natural period above the range ofaudibility, and a surrounding supporting portion.

31. A diaphragm adapted to vibrate in accordance with the complex wavesof sound vibrations comprising a central portion adapted to vibrate as aunit, and so stressed that its resultant period of vibration issubstantially above the limits of audition, and 1 a resilient peripheralportion.

Signed at Seattle, King county, VVashington, this 29th day of September1926.

GARRISON BABCOCK.

